Surface hydrophobic modification of TiO2 and its application to preparing PMMA/TiO2 composite cool material with improved hydrophobicity and anti-icing property

Abstract

A white functional methyl methacrylate film filled with titanium dioxide for building roof and exterior wall is introduced. The film has excellent cooling performance, sunlight reflection performance and anti-icing performance. In our study, hydrophobic modification was carried on titanium dioxide (TiO2) to prepare functional composite films based on poly (methyl methacrylate) (PMMA). Herein, the nature of TiO2 successfully changed from hydrophilic to hydrophobic with the assistance of 3 wt% stearic acid, which was acknowledged by Fourier transform infrared spectroscopy and thermogravimetric analysis. Compared with unmodified TiO2, the contact angle of the modified TiO2 powder was increased from 27° to 132°, and the freezing delay time was significantly enhanced from 6 s to 1284 s at −10 °C. In addition, the contact angle, solar reflectivity and cooling performance of PMMA/TiO2 composites with different content of modified TiO2 were investigated. Compared with PMMA/TiO2 composite film introduced with 50 wt% unmodified TiO2, the contact angle of that with 50 wt% modified TiO2 raised from 85° to 115°, while the freezing delay time enhanced from 184 s to 555 s at −10 °C. Contrast with pure PMMA film, the solar reflectance and cooling performance of PMMA/TiO2 composite film with 50% TiO2 were ameliorated greatly. The reflectivity ascended by 57.3% and 42.4% in the visible and near infrared regions, respectively. Simultaneously, the final temperature of the corresponding sample was decreased by 6.3 °C in outdoor temperature test in comparison with PMMA, performing great cooling property. The as-prepared cool material is expected to be widely applied in construction for its improved hydrophobicity and anti-icing character.